Influence of Rotor Closed Slots on Magnetic Field Harmonics and Electromagnetic Vibration in Induction Motors

The application of closed slots in the rotors of induction motors has been explored by researchers as a means to reduce vibration by weakening the magnetic field harmonics associated with slotting. However, the magnetic field harmonics resulting from the saturation of the closed-slot bridge are often overlooked in motor vibration optimization. In this paper, a comparative analysis of the magnetic field harmonic distributions in motors with both semiclosed and closed slots is presented. While the attenuation of slot harmonics is confirmed, it is also observed that new electromagnetic force waves arise due to the saturation of the rotor's closed-slot bridge. These waves can, under certain conditions, intensify electromagnetic vibrations. This phenomenon has been validated through finite element simulations and experimental tests on actual machines, offering valuable insights for vibration reduction in induction motors.